This invention relates generally to scintillation detectors which are used, for example, to measure radiation at successive depths of bore holes in the earth and, more particularly, to a scintillation detector having a novel and improved hermetically sealed housing and which includes a novel and improved window assembly.
U.S. Pat. No. 4,004,151, assigned to the assignee of the present invention, discloses a scintillation detector of the type to which this invention relates. This patent describes in considerable detail the types of scintillation crystals employed in such devices, their operation, and requirements. Such patent is incorporated by reference for such disclosure.
In U.S. Pat. No. 4,004,151, a detector is disclosed in which a tubular case for encapsulating a crystal is closed by a plug or cap at one end and by a window mounted with epoxy at the other end. In addition, such patent discloses a structure in which the crystal is spring-loaded toward an optical coupling with the window. A purpose of such spring-loading structure is to allow thermal expansion of the crystal relative to the case resulting from the fact that the crystal has a much higher coefficient of thermal expansion than the case material.
The principal purpose of such encapsulation structure is to provide a hermetically sealed enclosure for the scintillation crystal to prevent the crystal and other internal parts of the assembly from being damaged by exposure to the detector's environment. For example, such crystals are usually highly hygroscopic and are damaged if exposed to moisture.
In a related copending application Ser. No. 185,292, filed Sept. 8, 1980, now U.S. Pat. No. 4,360,733, an improved window mounting structure is disclosed in which an adhesive such as epoxy is used to secure the window in a retaining ring adapted to be welded to the window end of a scintillation detector case.